The present invention relates to a method for manufacturing a magnetic tape cassette incorporating and holding therein freely rotatable tape winding members or hubs and having upper and lower half cases formed from a synthetic resin.
Conventional magnetic tape cassettes such as those for audio and video equipment, computers and the like, include a magnetic tape wound around a tape winding member or members, for example, a hub, a reel or the like, such that the magnetic tape can be continuously advanced for recording and/or playback.
Conventional magnetic tape cassettes as described above typically include upper and lower half cases each formed from a synthetic resin such as acrylonitrile-butadiene-styrene copolymer resin (hereinafter referred to as "ABS" resin) or the like.
An audio tape cassette is an example of the conventional cassettes described above. As shown in FIG. 6, this magnetic tape cassette 41 is constructed such that a pair of hubs 43a and 43b, each having a magnetic tape wound therearound, are rotatably mounted in and held by a case body composed of upper and lower half cases 41a, 41b formed from ABS resin. After the upper and lower half cases 41a, 41b are respectively molded, the half cases are fastened together by a plurality of screws 44 (five screws as depicted in FIG. 6).
Conventional magnetic tape cassettes, one example of which includes the audio tape cassette above, contain relatively small-sized parts such as the screws 44 in FIG. 6. Furthermore, the conventional cassette case requires boss portions into which the screws 44 are inserted and recessed portions which prevent the heads of the screws 44 from projecting above the surface of the cassette. As a result, the cassette case has a relatively complicated structure.
Furthermore, in fastening the upper and lower half cases 41a, 41b together by means of screws 44, uneven contact pressures result between the contact surfaces of the upper and lower half cases in accordance with the fastening forces. For example, in the vicinity of the screws 44, the contact pressures are high. By way of contrast, the contact pressures are lowest at a midpoint between adjacent screws.
Furthermore, the fastening pressures on the contact surfaces of the upper and lower half cases 41a, 41b will vary in accordance with temperature changes in the environment in which the cassette is used. The tape cassette 41 may therefore be easily deformed especially with respect to relatively large cassette cases, such as VHS tape cassettes, where the distance between adjacent screws is typically 160 mm or more.